Method of forming shrink film package



Sept. 20, 1966 R. -r. WALTER METHOD OF FORMING SHRINK FILM PACKAGE FiledDec. 16. 1963 fnz/enjbrr l1 ickardf z /ali'er 1 WW United States Patent3,273,302 METHOD OF FORMING SHRINK FILM PACKAGE Richard T. Walter,Norristown, Pa, assignor to Container Corporation of America, Chicago,11]., a corporation of Delaware Filed Dec. 16, 1963, Ser. No. 330,680 3Claims. (CI. 53-39) The present invention relates to a method of formingpackages which include an outer wrapping of shrinkable film and moreparticularly to the production of packages of this type formed with aneasy opening feature.

Among the important objects of the invention are to provide a package ofrelatively simple construction, which is easy to produce, and whichincludes a thin, snugly engaging, enclosing film or wrapper havingprovision by which such film may be readily torn away along well definedlines to afford ready access to the contents.

Additional and more specific objects and advantages of the presentinvention will become apparent as the description proceeds.

In the drawings:

FIGURE 1 is a perspective view of a carton which is to be wrapped;

FIGURE 2 is a perspective view of the carton after being wrapped with asheet of shrinkable film the edges of which have been brought togetherand sealed;

FIGURE 3 is a perspective view of the carton after the film wrapping hasbeen subjected to conditions, such as heat, causing the film to shrinkand enclose the carton closely on all sides;

FIGURE 4 is a view similar to FIGURE 3 showing the end portion of thewrapper treated by creating a cut or severance in the form of a pull tabwhich may be grasped by the fingers;

FIGURE 5 is a view similar to FIGURE 6 showing the tab after it has beenlifted and pulled to disrupt the film at the top of the cartonpreparatory to obtaining access to the contents of the carton;

FIGURE 6 is a perspective view of a modified form of film wrappershowing the provision of weakened or partially severed lines in the filmcovering the top of the carton to give more exact control of the tearproduced when the pull tab is lifted; and

FIGURE 7 is a fragmentary perspective view showing the use of a heatedtool to be employed in cutting the film at the end of the carton.

The present invention is exemplified by the application of a film ofthermoplastic material to an open top egg carton which is designed toalford adequate protection to the eggs packed therein and at the sametime permit the eggs to be easily viewed by the purchaser. It is to beunderstood, however, that the invention may be applied to any form offilled carton or similar article.

As shown in FIGURE 1, the carton 5 is made ready for its wrapping bysetting it up and filling it with desired contents. The carton may thenbe enclosed in a wrapper comprising a shrinkable film of thermoplasticmaterial, indicated at 6, which may be in the form of a sheet, the edgeportions of which are brought together at the ends and along one side ofthe filled carton and are heat sealed in a well known manner by applyingheated elements to form seams indicated at 6a and 6b.

The loosely wrapped package may then be placed in or passed through asuitable heated area for a short period which will cause the film toshrink and form a tight or snug fitting wrapper around the entirecarton, as illustrated in FIGURE 3. Any material having heat shrinkingcharacteristics may be utilized for this purpose, such asheat-shrinkable polypropylene or poly- ICC vinylidene chloride film, thelatter being commercially distributed under the trade name Saran.

In order to provide easy opening means, one of the panels of thewrapper, held tensioned around the carton, is formed with a suitable cutby means of which tearing of the wrapper may readily be started. Asshown in FIGURES 4 and 7 the portion of the Wrapper at one end of thecarton may be cut in the form of a pull-tab 7 by means of a U-shapedtool 8 which has been heated to a temperature which will cause thematerial of the film to fuse. Thus, there is produced a cut line 9 alongwhich the film is separated and the fused material has gathered alongthe opposite edges of the cut. By forming a tab in this manner after atransparent thermoplastic wrapper has been applied to the carton andbrought under tension by shrinking it, the tab thus can be formed inexact registration with suitable printing on the carton which showsthrough the transparent film.

When it is desired to remove the contents from the wrapped carton asshown in FIGURE 7, this may be done after first lifting the tab 7 andpulling it in a direction lengthwise of the package as shown in FIGURE 5which will cause a strip 10 to be torn from the tensioned top panel ofthe wrapper.

In order to provide for a reasonably accurate tearing operation it isdesirable to wrap the carton with the sheet of thermoplastic material sothat the grain of the material will extend lengthwise of the top panelof the carton.

As shown in the modified form of wrapper, illustrated in FIGURE 6, apair of weakened lines 11, 11 may be formed by passing a heated tool ofproper configuration lengthwise of the top panel to produce a pluralityof closely spaced small openings or slots. These weakened lines will beformed so as to terminate adjacent the ends of the U-shaped cut formingthe pull talb indicated at 7a in FIGURE 6. By this construction a moreaccurate tear strip may be formed in the top panel of the wrapper and itis not important to arrange the wrapping sheet so that the grain of thesheet extends lengthwise of the top panel.

When a strip of material has been removed from the top of the wrapper,as illustrated, it is a simple matter to remove or tear the wrapperfurther to give ready access to the contents of the package.

While the present description sets forth preferred forms of theinvention, various changes may be made in the constructions disclosedwithout departing from the spirit of the invention, and it is there-foredesired that the present disclosure be considered in all respects asillustrative and not restrictive, reference being had to the appendedclaims rather than to the foregoing description to indicate the scope ofthe invention.

I claim:

1. A method for forming a package comprising a filled carton encased ina thermoplastic film element, which comprises:

(a) enclosing the filled carton relatively loosely within athermoplastic film element;

(b) shrinking such film element to tighten it around the filled carton;and

(c) perforating the film element to provide tear strip openings.

2. A method for forming a package comprising a filled carton encased ina thermoplastic film element, which comprises:

(a) enclosing the filled carton relatively loosely within an element ofheat-shrinkable thermoplastic film; (b) shrinking such film element bymeans of heat to tighten it around the filled carton to produce tensionin at least one area of the film; and (c) applying a disrupting amountof heat to a re- D stricted pattern in the tensioned area to produce acut in the form of a pull tab by which a portion of the Wrapper mayreadily be torn.

3. A method for forming a package comprising a filled, rectangularshaped carton encased in a thermoplastic film element, which comprises:

(a) enclosing the filled carton relatively loosely within an element ofshrinkable film;

(b) shrinking such film element to tighten it about the filled carton toproduce tension in at least two adjoining panels of the enclosing film;

(c) applying with a heated tool a disrupting amount of heat to form acut in the shape of a pull tab in one tensioned panel near its line ofconnection with the second tensioned panel; and

(d) applying with a heated tool a disrupting degree of heat to form inthe second tensioned panel two approximately parallel lines of spacedcuts extending from points near the extremities of the pull tab 4 asubstantial distance across said second tensioned panel.

References Cited by the Examiner UNITED STATES PATENTS 2,261,875 11/1941Dunn 215-38 2,322,594 6/ 1943 Russell 2.2951 2,533,738 12/1950 Moore20645.33 2,554,841 5/1951 Rumsey 206-4533 3,001,644 9/1961 Fourness etal. 229-51 3,041,802 7/1962 Cummings et al 5339 3,084,489 4/ 1963Seefluth 53-39 3,111,221 11/1963 Chapman et al 20665 GRANVILLE Y.CUSTER, 111., Primary Examiner.

THEROIN E. CONDON, Examiner.

W. T. DIXSON, Assistant Examiner.

1. A METHOD FOR FORMING A PACKAGE COMPRISING A FILLED CARTON ENCASED INA THERMOPLASTIC FILM ELEMENT, WHICH COMPRISES: (A) ENCLOSING THE FILLEDCARTON RELATIVELY LOOSELY WITHIN A THERMOPLASTIC FILM ELEMENT; (B)SHRINKING SUCH FILM ELEMENT TO TIGHTEN IT AROUND THE FILLED CARTON; AND(C) PERFORATING THE FILM ELEMENT TO PROVIDE TEAR STRIP OPENINGS.